1. Field of the Invention
The present invention relates to a photo-detector array for detecting an image signal of an infrared laser radar and a method of manufacturing the same, and more particularly, to a two-dimensional avalanche photo-detector array having a planarized surface, for detecting an image signal of an eye-safe infrared laser, and a method of manufacturing the same.
2. Description of the Related Art
A photo-detector array for detecting an image signal of an eye-safe infrared laser radar having a wavelength band of 1.55 μm includes a number of photo-diodes. The discrete photo-detector includes a semi-insulating InP substrate, a n+-InP layer, an n-InGaAs, n-InGaAsP layer, and n-InP layer layer sequentially stacked on the semi-insulating InP substrate. A photo-absorbing layer is formed in the n-InGaAs layer, and photo-diode amplification region is formed on the n-InP layer where the PN junction is formed. The photo-diodes form unit cells of the photo-detector array, respectively.
The unit cells of the photo-detector must be electrically isolated for the independent electrical access, and a conventional photo-detector uses a trench for this purpose. The trench is a so-called mesa type groove, and is formed by partially etching the n-InGaAs layer and the n+-InP layer.
However, since the unit cells of a conventional photo-detector array are isolated by the trench, metal wiring for connecting p-type electrodes formed on a p+ diffusion region has to be extended over an inner surface of the trench, and thus the path length of the metal wiring becomes long. As a result, signal delay or signal distortion may occur, and the arrangement of the metal wiring may be complicated. Furthermore, since the isolating trench has a deep and narrow shape, the metal wiring in the inner surface of the trench may not be regularly deposited and it may even be disconnected, thereby deteriorating the reproducibility and reliability of a product.
Furthermore, since the trench is used to isolate devices, a side of the p-n junction is exposed outwardly by the trench, thereby causing leakage current.
Accordingly, the photo-detector needs an isolation structure in which the metal wirings between discrete photo diode cells are formed over the electrically isolated flat surface made possible with embedded isolation structure using ion implantation into the semiconductor.